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Green or sprouting potatoes are toxic – true or false?

True and false. Here’s what you need to know.

May 15, 2018

The “eyes” of a potato

The nodes or indentations in the skin of a potato are called “eyes”. These little indentations or nodes would grow new leaves and branches on the stem of a plant above ground. Potatoes are classified as tubers and they grow from the ends of underground stems below the roots of the potato plant. Each mature potato tuber has several stem buds from which new plants can sprout.

When these “eyes” are exposed to warmth and moisture they sprout into entire stems with roots growing from their bases and leaves at the tops.

Can you eat a potato that has sprouted?

When potatoes sprout, the starch in the potatoes is converted into sugar. If the potato is firm, most of the nutrients will be intact and it can be eaten after cutting out the sprouted part. If the potato is shrunken and wrinkled, it should not be eaten. The growth process will trigger the assimilation of the sugars and vitamins which would make the potato less nutritious.

Can you eat a potato that has turned green?

Green potatoes do contain a form of toxin, but you are unlikely to ingest enough of it to do any harm. A healthy adult would have to eat about 2 kg of green potatoes to experience symptoms.

Exposure to light triggers the production of chlorophyll which causes the green colour. Potatoes that have turned green can potentially contain a naturally occurring toxin called Glycoalkaloids (GA). This bitter chemical is part of the plant’s defenses against insects, disease and predators. Cutting away the green area eliminates most of the GAs.

Light and warmth also trigger the production of solanine – a chemical which can cause symptoms of poisoning in humans if ingested in large quantities. Symptoms include nausea, diarrhoea, vomiting, stomach cramps, burning of the throat, headaches and dizziness. Solanine tends to be concentrated under the skin of the potatoes alongside the chlorophyll and also in the newly developing sprouts.

Removing the green peel and the sprouting shoots will reduce the chances of a toxic reaction, but potatoes that have begun to grow can have a bitter taste.

Storing potatoes

Potatoes should be stored in a well-ventilated, cool, dry, dark place for maximum shelf life. You can place them in a paper bag or cardboard box (not in a plastic bag). Do not store them in a refrigerator. Buy only enough potatoes for a week at a time.